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Case report

Sequential occurrence of thrombotic thrombocytopenic purpura, essential thrombocythemia, and idiopathic thrombocytopenic purpura in a 42-year-old African-American woman: a case report and review of the literature

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Comments on �� Sequential occurrence of thrombotic thrombocytopenic purpura, essential
thrombocythemia, and idiopathic thrombocytopenic purpura in a 42-year-old African-American
woman: a case report and review of the literature��

To the Editor: I read this case report with interest and would like to give some comments.

Firstly, the authors did not mention in the case report the degree of schistocytosis,
other blood smear findings, results of reticulocyte count, direct antiglobulin test
(DAT), lactate dehydrogenase, haptoglobin, prothrombin time and activated partial
thromboplastin time in 1994. They also did not mention computed tomography findings
of the brain. Presence of schistocytes per se is not diagnostic of thrombotic thrombocytopenic
purpura (TTP) as schistocytes can even be seen in normal people and in other conditions.
Burns et al reported that schistocytes can be seen in 58% of normal people with a
mean of 0.05% (range 0-0.27%) of all red cells while TTP patients have more schistocytes
with a mean of 5% (range 1.1-9.4%) [1]. In this case, if the DAT test had been reported
positive with IgG together with small amount of schistocytes, the diagnosis might
have been changed to warm autoimmune hemolytic anemia with immune thrombocytopenic
purpura (ITP). There have been many case reports of warm autoimmune hemolytic anemia
and ITP responding to plasmapheresis [2- 4]. Efficacy of plasmapheresis in those
disorders is due to removal of the autoantibodies. It is also noted that JAK-2 positive
latent myeloproliferative disorders (MPD) can present with stroke and other thromboses
several years before developing into overt MPD [5- 7].

Secondly, the authors did not mention the white cell count, red cell count, hemoglobin
and hematocrit levels in March 2001. The presence of thrombocytosis, clustering megakaryocytes
and cellularity of the marrow per se is not diagnostic of essential thrombocythemia
[ET]. So also, the authors did not describe the morphology of the erythroid and granulocytic
series as well as the status of the stainable iron in the bone marrow for March 2001.
Later in October 2001, the patient was found to have absent stainable iron in the
bone marrow. Had she had absent stainable iron in the bone marrow in March 2001, she
might as well have masked polycythemia vera (PV) as coexisting iron deficiency anemia
could bring down the hemoglobin level to a normal level. Rarely, PV patients can
present with anemia [8]. Of note, positive JAK-2 mutation status is not unique to
ET alone and can be seen in other MPD including PV [9]. So also, autoimmune hemolytic
anemia and ITP can be seen in patients with MPD [10-12]. ET and PV can also eventually
evolve into myelofibrosis.

Finally, I would like to point out that there are many missing points in this case
report due to the reasons mentioned above. Rather than reporting the extremely small
possibility of the occurrence of three platelet disorders albeit sequentially in this
patient, would not it be reasonable to try to unify those diagnoses. This patient
certainly has MPD of some kind due to positive JAK-2 mutation although I am not sure
about the certainty of the ET diagnosis. Due to response of low platelet count to
intravenous immune globulin, I believe she also had ITP. However, whether she truly
had TTP in 1994 was not clear due to paucity of clinical data in this report.